Messages in this thread |  | | Date | Sun, 4 Dec 2022 00:20:37 +0000 | From | Gary Guo <> | Subject | Re: [PATCH v2 05/28] rust: macros: add `concat_idents!` proc macro |
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On Fri, 2 Dec 2022 17:14:36 +0100 ojeda@kernel.org wrote:
> From: Björn Roy Baron <bjorn3_gh@protonmail.com> > > This macro provides similar functionality to the unstable feature > `concat_idents` without having to rely on it. > > For instance: > > let x_1 = 42; > let x_2 = concat_idents!(x, _1); > assert!(x_1 == x_2); > > It has different behavior with respect to macro hygiene. Unlike > the unstable `concat_idents!` macro, it allows, for example, > referring to local variables by taking the span of the second > macro as span for the output identifier. > > Signed-off-by: Björn Roy Baron <bjorn3_gh@protonmail.com> > Reviewed-by: Finn Behrens <me@kloenk.dev> > [Reworded, adapted for upstream and applied latest changes] > Signed-off-by: Miguel Ojeda <ojeda@kernel.org> > --- > rust/macros/concat_idents.rs | 23 +++++++++++++++++++ > rust/macros/lib.rs | 44 ++++++++++++++++++++++++++++++++++++ > 2 files changed, 67 insertions(+) > create mode 100644 rust/macros/concat_idents.rs > > diff --git a/rust/macros/concat_idents.rs b/rust/macros/concat_idents.rs > new file mode 100644 > index 000000000000..7e4b450f3a50 > --- /dev/null > +++ b/rust/macros/concat_idents.rs > @@ -0,0 +1,23 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +use proc_macro::{token_stream, Ident, TokenStream, TokenTree}; > + > +use crate::helpers::expect_punct; > + > +fn expect_ident(it: &mut token_stream::IntoIter) -> Ident { > + if let Some(TokenTree::Ident(ident)) = it.next() { > + ident > + } else { > + panic!("Expected Ident") > + } > +} > + > +pub(crate) fn concat_idents(ts: TokenStream) -> TokenStream { > + let mut it = ts.into_iter(); > + let a = expect_ident(&mut it); > + assert_eq!(expect_punct(&mut it), ','); > + let b = expect_ident(&mut it); > + assert!(it.next().is_none(), "only two idents can be concatenated"); > + let res = Ident::new(&format!("{a}{b}"), b.span()); > + TokenStream::from_iter([TokenTree::Ident(res)]) > +} > diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs > index 91764bfb1f89..15555e7ff487 100644 > --- a/rust/macros/lib.rs > +++ b/rust/macros/lib.rs > @@ -2,6 +2,7 @@ > > //! Crate for all kernel procedural macros. > > +mod concat_idents; > mod helpers; > mod module; > > @@ -70,3 +71,46 @@ use proc_macro::TokenStream; > pub fn module(ts: TokenStream) -> TokenStream { > module::module(ts) > } > + > +/// Concatenate two identifiers. > +/// > +/// This is useful in macros that need to declare or reference items with names > +/// starting with a fixed prefix and ending in a user specified name. The resulting > +/// identifier has the span of the second argument. > +/// > +/// # Examples > +/// > +/// ```ignore > +/// use kernel::macro::concat_idents; > +/// > +/// macro_rules! pub_no_prefix { > +/// ($prefix:ident, $($newname:ident),+) => { > +/// $(pub(crate) const $newname: u32 = kernel::macros::concat_idents!($prefix, $newname);)+ > +/// }; > +/// } > +/// > +/// pub_no_prefix!( > +/// binder_driver_return_protocol_, > +/// BR_OK, > +/// BR_ERROR, > +/// BR_TRANSACTION, > +/// BR_REPLY, > +/// BR_DEAD_REPLY, > +/// BR_TRANSACTION_COMPLETE, > +/// BR_INCREFS, > +/// BR_ACQUIRE, > +/// BR_RELEASE, > +/// BR_DECREFS, > +/// BR_NOOP, > +/// BR_SPAWN_LOOPER, > +/// BR_DEAD_BINDER, > +/// BR_CLEAR_DEATH_NOTIFICATION_DONE, > +/// BR_FAILED_REPLY > +/// ); > +/// > +/// assert_eq!(BR_OK, binder_driver_return_protocol_BR_OK); > +/// ``` > +#[proc_macro] > +pub fn concat_idents(ts: TokenStream) -> TokenStream { > + concat_idents::concat_idents(ts) > +}
Reviewed-by: Gary Guo <gary@garyguo.net>
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